Safety joint



May 28,1940. F. N. OSMUN 2,202,261

SAFETY JOINT Filed Aug. 23. 1937 fired N Usmun Patented May 28, 1940 UNIT-ED STATES ..PATEN1-,oFFlcr-:

SAFETY JOINT Fred N` Osmun, Houston, Tex. Application August 23, 1937, serial 10,160,453 claims. (ci. Z55-2s) becomes stuck in th bore and can not be\ withdrawn and in such event, it is desirable to unscrew, withdraw and save the drill stem. The safety joint herein described may be located in the stem adjacent the drill so that in case the drill becomes stuck thestem may be parted at the safety joint, and, as hereinafter described,

withdrawn and thus recovered.

It is one of the principle objects of the invention to provide a safety joint of thecharacter described which is not liable to become unscrewed during ordinary drilling operations but which may be readily unscrewed in case of necessity and when it is desired to separate the drill stem and withdraw it.

Duringdrilling operations it often happens that the drill becomes temporarily stuck or held against rotation and in such case when the drill stem is-placed under torsional strain, suflicient to release the drill, it causes the lower portion of the stem to spin, sometimes resulting in the accidental unscrewing of a conventional type of safety joint, if the same is used. With the improved type of safety joint herein described, this is not possible for the reason that the relatively rotatable parts of the joint are locked against unscrewing until it is desired to release the same to permit the separation of the stem.

It is a further object of the invention to provide a safety joint of the character described whose parts, or sections, are connected by a novel type of thread of such construction that it. will' 'specification and illustrated in the accompanying drawing, wherein:r

Figure 1 shows a side view, partly in section, of one form of the safety joint.

Figure 2 shows a cross sectional view thereof, 5 ,taken on the line A-A of Figure 1.

Figure.3 shows an enlarged fragmentary side view of the pin member.

Figure 4 shows a side view, partly in section, of another embodiment, and

Figure 5 shows a cross sectional view taken on the line B-B of Figure 4. l

Referring now more particularly to the drawing, wherein like numerals of reference designate the same parts in each of thevfig'ures, the l5 numeral I designates a driving member such as a drill stem used for rotary well drilling. As is well known, the drill stem is made up of sections connected by threads. It is driven from the rotary at the ground surface and drives-the drill at- 20 tached to the lower end thereof. The type of safety joint shown in .Figure 1 is preferably incorporated into the drill stem just aboveA the drill. although it maybe incorporated into the `stem.

at any point. It embodies a box member 2, at- 23 tached to the lower end of the stem proper, and

a pin member 3, whose lower end is threaded for connection to a drill collar or other coupling beneath. The pin member 3 ls threaded into the box member 2. The interconnecting threads 30 embody spiralled scrolls l, 5, the former in the box member 2 and the latter on the pin member The scroll like threads 5 fit nicely ,in the corresponding threads 4 when the parts are screwed 36 together. The box and pin members 2 and 3 also have the opposing faces 6 and l which are pitched" reversely with respect to the pitch of said threads and which abut when the pin is screwed home into the box and which, upon further relative 40 rotation of the pin andbox, effect a relative endwise movement of the connected parts, so `asto distribute the torsional strain' and to prevent the parts from becoming screwed too tightly together, thus eliminating any tendency of the 45 threads to "freeze or gall.

The upper end of thepin member 3, may be tapered and formed with teeth asf8 and threaded into the upper end `of the pin there is a tubular nipple 9. l

Within the box member 2 there is a tubular plunger I0 mounted on the upper end of which there is an upwardlyopening cup ring Il 'which forms a close tting joint with the inner wall of the box member 2. The lower end of the plunger 63' III fits over the nipple 9 and there may be an annular packing I2 countersunk into said plunger and fitted closely around said nipple. The lower end of the plunger is flared and formed with teeth I3 arranged to intermesh with the teeth 8 as shown in Figure 1. The plunger I0 has external.- vertical keys I4 which work in keyways I5 in the box member 2. 'Ihese keyways I5 are cut in the inwardly thickened portion of the box member 2, the upper end of said inwardly thickened portion forming an inside annular shoulder I6. The upper end of the plunger I 0 has an external annular ange Il and interposed between the shoulder I6 and flange I1 there is a coil spring I8 which normally holds the plunger I0 elevated and the teeth I3 out of mesh with the teeth 8. During ordinary drilling operations drilling fluid is forced under pressure down through the drill stem. The pressure of the drilling fluid holds the plunger I0 in its lower position with the spring I8 compressed and with the teeth I3 engaged with the teeth 8. 'I'he box 2 and pin 3 are thus positively locked against unscrewing. Should the drill, or the portion of the drill stem beneath the safety joint, become stuck, the pump for forcing the drilling fluid down through the drill stem may be stopped whereupon, the pressure being relieved, the spring I8 will immediately elevate the plunger I0 and release the teeth I3 from the teeth 8. The weight of the drill stem may then be released, that is, the drill stem above the safety joint may be permitted to move downwardly and the sloping face 6, riding on the sloping face 1, will cause the box member 2 to turn to the left slightly, thus breaking the joint. In other words, the column stress of the drill stem above the safety joint will cause the safety joint to partially unscrew or break. 'I'he drill stem may then be safely reversed, or turned to the left, and it will part at the safety joint without danger of being separated at one of the joints connected by the ordinary threads. The operator is thus enabled to part the drill stem and recover the major portion thereof should the drill become so tightly stuck that it can not be recovered. In the form shown in Figure 4 and Figure 5, the plunger Ia has an external annular shoulder I6a and a coil spring I8a surrounds the upper end of the plunger |0a and is interposed between the shoulder IBa and the lower end of the section of tl'e drill pipe above. This spring normally holds the teeth I3 of the plunger in mesh with the teeth 8 at the upper end of the pin 3. Beneath the shoulder I6a the box member 2a has the inside vertical keys Ma which are received by the external vertical keyways I5a in the plunger, whereby said parts are permitted to relatively move longitudinally butare locked against relative rotation. l

In thisy form the spring I8a will at all times maintain the teeth' I3 in mesh with the teeth 8, thus locking the pin and box against unscrewing. Should the drill, or drill stem become stuck, a suitable grappling tool may be lowered down through the drill stem and engaged with the plunger Illa and said plunger pulled upwardly to release the intermeshing teeth and thereupon, upon reverse rotation of the drill stem, the safety joint will be readily unscrewed as before and the drill stem thus recovered. It is obvious that the type of safety joint shown in Figure 4 may be located at different points in the drill stem and if the drill stem is stuck in such manner that upon release of one of the lower safety joints the stem can not be pulled, one of the safety joints above may be released and that portion of the drill stem above then backed off and recovered.

The drawing and description disclose what is now considered to be preferred forms of the invention by way of illustration only, while the broad principle of the invention will be defined by the appended claims.

What I claim is:

1. A safety joint comprising a box member, a pin member having la threaded connection with the box member, a slidably mounted locking device in the box member movable into one position to interlock with the pin member and into another position to release the pin member and a yieldable member for moving said locking device into released position.

2. A safety joint comprising a tubular box, a pin screwed into the box, a slidably mounted locking device in the box, said pin and locking device having intermeshing teeth whereby they may be locked against relative rotation when the locking device is in active position and released when the locking device is in inactive position, means for preventing rotation of the locking device relative to the box, yieldable means formoving the locking device into inactive position and means adapted to be actuated by fluid under pressure to move said locking means to active position.

` 3. A safety joint comprising a tubular box, a tubular pin threaded into the box, a tubular plunger slidably mounted in the box and anchored against rotation relative to the box, said plunger and pin having teeth adapted to intermesh upon application of uid under pressure to the plunger and yieldable means normally maintaining said teeth out of mesh.

4. A safety joint comprising two tubular parts, one of said parts being formed with an internally threaded box and the other of said parts being formed with an externally threaded pin adapted to be screwed into the box, a plunger having a slidable splined connection with the box, said plunger and pin having intermeshing parts adapted to intermesh, upon application of fluid under pressure to the plunger, to lock the pin against rotation relative to the box and yieldable means normally holding said intermeshing parts in released position.

5. A safety joint comprising two tubular parts,

one of said parts being internally threaded and the other part an externally threaded pin adaptyed to be screwed into said internally threaded FRED N. osMuN. 

